1. Field of the Invention
The present invention is directed to controlling the flow of current from a battery and, more particularly, to controlling the flow of current from a rechargeable battery by way of an automatic circuit breaker which interrupts the flow of current from the battery upon the development of a predetermined overcurrent, with a device resistance of less than or equal to 0.2 milliohms.
2. Related Art
Batteries in the related art include circuit breakers for stopping the flow of current from the battery upon a predetermined condition. In particular, U.S. Pat. No. 4,188,460 to Kang et al. discloses an internal battery fuse in which excessive built-up heat resulting from a short circuit is concentrated in a portion which then heat fuses and interrupts the circuit. The heat fusible portion is formed as a thinned strip making up a portion of the current collector and is surrounded by a heat shield. When current exceeds a predetermined threshold, the thinned strip provides a greater electrical resistance than the rest of the current collector, and thus heats up. Because the shield retains the heat around the thinned strip, the thinned strip fuses to break the electrical connection within the current collector thus terminating current flow from the battery. Alternatively, the thinned strip may be a separate element which is welded between two portions of the current collector. However, Kang includes the disadvantage that the circuit is broken at a point within the cell itself. That is, the heat fusible portion is located adjacent the electrode stack which produces gasses that may be ignited by any arcing in the fusible portion. Further, because Kang requires a heat shield as well as either a thinned portion of an elongate strip current collector or a thinned strip welded to different portions of the current collector, his battery fuse is complex.
U.S. Pat. No. 4,690,879 to Huhndorff et al. and U.S. Pat. No. 5,057,382 to Tucholski also disclose complex mechanisms for interrupting the flow of current from a battery. In each of these batteries, the current flow is terminated upon the bulging of the cell due to excessive pressure therein. When pressure builds up within either battery, the ends bulge. In Huhndorff, the current is terminated due to a break in a weld connection between a cover terminal and a metal container upon the battery's bulging. In Tuchoski, the current is interrupted by the relative sliding movement between a secondary conductive cover and a container contact member upon the battery's bulging.